JP2003281991A - Hot cathode and discharge apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve manufacturing yield and durability of a hot cathode discharge apparatus by preventing a diamond from peeling off an electrode. <P>SOLUTION: The discharge apparatus comprises an enclosure 10 in which a discharge gas is sealed up, and hot cathodes 11a and 11b disposed in the enclosure 10. The hot cathodes 11a and 11b comprise an electrode, a first member which is provided on the surface of an electrode of the electrode and comprises a carbon containing SP2 hybrid orbital coupling, and a second member which is provided on the surface of the first member and comprises diamond. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot cathode and a discharge device using the same, and more particularly to a hot cathode used for illumination and the like and a discharge device using the same.

[0002]

2. Description of the Related Art FIG. 10 shows the structure of a conventional general hot cathode discharge lamp. As shown in this figure, the conventional general hot cathode discharge lamp has a glass tube 100 coated with a phosphor 102.
, A pair of electrodes (filaments) 101a and 101b attached to both ends of the glass tube, and lead wires 101c and 1
01d and a pair of metal fittings 104a and 104b. Introducing lines 101c and 101d are electrodes 101
a and 101b for holding and energizing, respectively, and held by a pair of metal fittings 104a and 104b, respectively. The electrodes 101a and 101b are double or triple.
An electron emitting material called an emitter is applied to a heavy coiled filament. Argon or a mixed rare gas and a small amount of mercury are sealed as a sealing gas 103 in the glass tube at a pressure of 2 to 4 hPa to facilitate discharge.

During discharge, when current is applied to the electrodes 101a and 101b to preheat them, electrons are emitted from the emitter that has become high in temperature. The emitted electrons move to the counter electrode (anode) and the discharge starts. Here, generally, an AC voltage is applied to the electrodes 101a and 101b in order to generate discharge, and when one of the electrodes 101a and 101b acts as an emitter, the other electrode is a counter electrode (anode).
Acts as. Electrons are generated in the glass tube 100 by this discharge.
Collide with mercury atoms sealed inside. Mercury atoms receive energy by collision and emit ultraviolet rays. The ultraviolet light excites the phosphor 102 to generate visible light. The emission color differs depending on the type of phosphor, and light of various color types such as white, daylight, and blue is emitted from the lamp.

The filament during discharge reaches 1000 degrees or more, the emitter coated on the coil evaporates,
Upon being bombarded with ions or electrons, they are sputtered and consumed. The electron emission material diffuses into the glass tube by such evaporation or sputtering. The diffused electron-emitting substance adheres to the inner surface of the glass tube and reacts with mercury to form amalgam and blacken. This phenomenon not only spoils the appearance but also becomes a main cause of the decrease in the luminous flux of the lamp.

There are various means for preventing the consumption of the electron emitting material. For example, there is a structure in which an electron-emitting substance is made into diamond, which is a substance that is difficult to be sputtered (Japanese Patent Laid-Open No. Hei 10 (1999) -31977).
10-69868 and JP-A-2000-106130). FIG. 11 is a cross-sectional view showing this structure, which is an enlarged cross-sectional view showing the configuration of the electrodes 101a and 101b in FIG. As shown in FIG. 11, diamond particles 105b are attached to the electrode material 105a by coating. For coating and adhesion, for example, diamond particles are mixed with an organic solvent, the electrode material is immersed in this solution, and ultrasonic cleaning is performed.

However, according to the research conducted by the present inventor,
When diamond is used as the electron-emitting substance, although diamond etching or consumption due to sputtering is suppressed, the adhesion between the metal, which is the electrode material, such as tungsten and diamond, is poor, and the diamond often peels from the electrode. However, it was newly found that the manufacturing yield and durability of the discharge device such as a hot cathode discharge lamp were extremely poor.

[0007]

As described above, as described above,
Discharge devices such as hot cathode discharge lamps that use diamond as an electron-emitting substance have poor adhesion between electrodes and metals such as tungsten, and diamond is frequently peeled off from the electrode. The manufacturing yield and durability were extremely poor.

The present invention has been made in view of the above circumstances, and a hot cathode capable of preventing the diamond from peeling off from the electrode and improving the manufacturing yield and durability of the hot cathode discharge device, and the hot cathode. It is an object of the present invention to provide a used discharge device.

[0009]

(Means for Solving the Problems) (Structure) In order to solve the above-mentioned problems, the present invention provides an electrode and a first member made of carbon provided on the surface of the electrode and containing SP2 hybrid orbital bonds. A hot cathode comprising: a second member made of diamond and provided on the surface of the first member.

Further, the present invention is a discharge device comprising an envelope in which a discharge gas is sealed, and a hot cathode arranged in the envelope, wherein the hot cathode is an electrode. A discharge device comprising a first member made of carbon provided on the surface of this electrode and containing SP2 hybrid orbital bonds, and a second member made of diamond provided on the surface of this first member. I will provide a.

In the above-mentioned present invention, it is preferable to have the following configuration.

(1) The carbon of the first member also includes an SP3 hybrid orbital bond.

(2) The first member is made of amorphous carbon.

(3) The first member is provided on the entire surface of the electrode.

(4) The second member contains diamond particles.

(5) SP between the diamond particles
The carbon containing two hybrid orbital bonds is provided.

(6) The surface of the second member is formed as a rough surface, and the diamond particles and the SP are formed on the surface.
2 Exposed carbon containing hybrid orbital bonds.

(7) The carbon containing SP2 hybrid orbital bond provided between the diamond particles in the second member is made of the same material as the carbon containing SP2 hybrid orbital bond in the first member.

(8) The second member is made of diamond containing a donor impurity.

(9) The discharge gas contains a gas containing an element having a main emission peak of 200 nm or less.

(10) The discharge gas contains a rare gas and mercury.

(11) The discharge gas contains Xe.

(12) The discharge gas contains hydrogen gas.

(13) The discharge device is a discharge lamp.

(14) The discharge device is a plasma display.

(Operation) According to the present invention, SP2 is formed on the electrode.
A second member made of diamond is formed via a first member made of carbon containing a hybrid orbital bond, and between the electrode and the first member, between the first member and the second member. Since the respective adhesions are good (especially, carbon containing SP2 hybrid orbital bond and diamond are the same carbon system and mutual adhesion is very high), the second member made of diamond is separated from the electrode. The problem of peeling can be effectively prevented, and the durability of the discharge device can be significantly improved. When the first member is made of amorphous carbon, the above-mentioned adhesion is very high. In this case, the controllability of the film thickness of the first member is good and can be controlled on the order of several nanometers, which makes a large contribution to the effect of adhesion.

Furthermore, when diamond is used as an electron emitting substance in a discharge device using a hot cathode, since diamond has a high sputtering resistance, the electron emitting substance is consumed and the electron emitting substance is consumed due to sputtering by plasma during discharge. It is possible to improve the problem of peeling from the electrode. When the second member made of diamond is a continuous film, the above effect becomes remarkable because the continuous film protects the entire surface of the electrode.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic view showing the structure of a hot cathode discharge lamp according to the discharge device of the present invention. As shown in this figure, the hot cathode discharge lamp according to the present embodiment includes a glass tube 10 coated with a phosphor 12, a pair of electrodes 11a and 11b attached to both ends of the glass tube, and lead wires 11c and 11d. , A pair of metal fittings 14a and 14b. Introducing wires 11c and 11d are electrodes 1
1a and 11b are used for holding and energizing, respectively, and are held by a pair of metal fittings 14a and 14b, respectively. The electrodes 11a and 11b are formed by coating a double or triple coil-shaped filament (for example, made of tungsten) with an electron-emitting substance called an emitter. Argon or mixed rare gas and a small amount of mercury are used as the sealing gas 13 in the glass tube to facilitate discharge.
It is sealed with a pressure of 4 hPa.

During discharge, when current is applied to the electrodes 11a and 11b to preheat them, electrons are emitted from the high-temperature emitter. The emitted electrons move to the counter electrode (anode),
Discharge starts. Here, generally, an AC voltage is applied to the electrodes 11a and 11b in order to generate discharge, and when one of the electrodes 11a and 11b acts as an emitter, the other acts as a counter electrode (anode). To work. Due to this discharge, the electrons collide with the mercury atoms sealed in the glass tube 10. Mercury atoms receive energy by collision and emit ultraviolet rays. This ultraviolet light excites the phosphor 12 to generate visible light. The emission color differs depending on the type of phosphor, and light of various color types such as white, daylight, and blue is emitted from the lamp.

FIG. 2 is an enlarged sectional view showing the constitutions of the electrodes 11a and 11b, and is a view showing a characteristic constitution of the hot cathode according to the present invention. As shown in FIG. 2, an amorphous carbon-based thin film 22 is formed on the surface of an electrode material (filament or the like) 21 as a first member made of carbon containing SP2 hybrid orbital bonds. A diamond thin film 23 as a second member is further formed on the surface of the carbon-based thin film 22 in the form of a continuous film.

In the hot cathode of this embodiment, the polycrystalline diamond layer 23 is formed on the electrode material 21 via the carbon-based thin film 22, and the electrode material 21 and the carbon-based thin film 22 are formed.
Since the adhesion between the carbon-based thin film 22 and the polycrystalline diamond layer 23 is good, it is possible to effectively prevent the problem that the polycrystalline diamond layer 23 is separated from the electrode material 21. Is. Furthermore, since the polycrystalline diamond layer 23 has high sputtering resistance,
Even if the hot cathode is exposed to the discharge gas sputtering in the discharge device, the polycrystalline diamond layer 23, which is a continuous film, serves to protect the entire surface of the electrode material 21, so that the durability of the hot cathode is significantly improved. Is possible.

Next, a method of manufacturing a hot cathode in the hot cathode discharge lamp of this embodiment will be described. First, a linear or plate-like electrode material 21 made of tungsten or the like is prepared, and the electrode material 21 is placed in an electron cyclotron resonance plasma chemical vapor deposition (ECRCVD) apparatus, and the electrode material 2
An amorphous carbon-based thin film 22 as a first member on the surface of No. 1
It is formed by ECRCVD.

FIG. 6 is a sectional view showing the structure of the ECRCVD apparatus. As shown in FIG. 6, microwaves are introduced from the microwave head 62a through the microwave waveguide 62b and further into the reaction chamber 63 through the microwave introduction quartz window 64. An upper electromagnetic coil 67 and a lower electromagnetic coil 68 are arranged around the reaction chamber 63 as a magnetic circuit for plasma generation. 67 is an electromagnetic coil for plasma generation, and 68 is an electromagnetic coil for plasma focusing.

The reaction gas is introduced into the reaction chamber 63 through the reaction gas introduction port 65. Sample 60 (corresponding to electrode material 21)
Is installed on the heater stage 61. Heater stage 61
The support base can be adjusted up and down, and has a mechanism that can be adjusted to an optimum position. A high frequency power supply (not shown) for applying a bias to the substrate is connected to the heater stage 61. The pressure in the reaction chamber 63 is controlled by a pressure adjusting valve (not shown), and exhaust is performed by an exhaust system 66 of a turbo molecular pump and a rotary pump. 6
9 is a heater power supply.

Using the apparatus shown in FIG. 6, the carbon-based thin film 22
The film forming conditions for forming the film by ECRCVD are as follows. That is, with a microwave power of 50 W and a self-bias using an RF power source of -100 V, hydrogen gas (H ₂ )
Using a mixed gas having a flow rate of 10 sccm and a methane gas (CH ₄ ) flow rate of 1 sccm, under a pressure of 1 Pa and a temperature of 750 ° C.,
A carbon-based thin film 22 having a thickness of 50 nm was formed with a film forming time of 1 minute.

In this embodiment, the reaction gas is hydrogen or methane gas. CO gas or CO ₂ gas may be used as the carbon source. Further, it is possible to dope impurities such as nitrogen and phosphorus, which show n-type, as impurities. In addition, there is no problem even with impurities showing p-type such as boron. Further, the method for manufacturing the carbon-based thin film 22 is the same as the EC shown in
Not only the RCVD method, but also the radio frequency (RF) CVD method, the ion beam method, or the like can be used for manufacturing.

Next, the diamond thin film 23 is continuously formed. That is, the diamond thin film 23 is formed by the microwave plasma CVD method while the vacuum atmosphere is maintained while the sample 60 is held in the reaction chamber 63 of the ECRCVD apparatus shown in FIG. Here, film formation is performed by a method that does not use the electromagnetic coils 67 and 68 in the ECRCVD apparatus shown in FIG. No bias from the RF power supply is used. In this film formation, the heater stage 61 is heated by the heater power supply 65, and the sample 60 placed on the heater stage 61 is heated.

The film forming conditions for the diamond thin film 23 in this case are as follows. That is, microwave power is 4k
W, reaction gas pressure 13 kPa, hydrogen gas flow rate 400
A diamond thin film 23 having a thickness of 0.5 μm was formed in 90 minutes of film formation with sccm, a methane gas flow rate of 4 sccm, and a substrate temperature of 850 ° C.

In this embodiment, only hydrogen gas and methane gas were used for forming the diamond thin film, but phosphorus, nitrogen,
It is possible to dope impurities having n-type such as sulfur and impurities having p-type such as boron as impurities. In addition,
The n-type dopant will be described later in detail. Further, the method for forming the diamond thin film 23 is also a microwave plasma CV.
Not only the D method but also the ECRCVD method, the radio frequency (RF) CVD method or the like can be used.

The structure of the hot cathode manufactured by the above manufacturing method was examined by Raman spectroscopy. FIG. 7 shows the analysis result. FIG. 7A is a characteristic diagram showing the relationship between the Raman shift and strength of the diamond thin film 23, and FIG. 7B is a characteristic diagram showing the relationship between the Raman shift and strength of the carbon-based thin film 22. As shown in these figures, the diamond thin film 2
No. 3 has a sharp peak due to SP3 hybrid orbital coupling, and thus is crystalline. On the other hand, the carbon-based thin film 22 has a smooth peak due to each of the SP2 hybrid orbital bond and the SP3 hybrid orbital bond, and it can be seen that the carbon-based thin film is an amorphous carbon-based thin film or a carbon-based thin film containing microcrystals. In FIG. 7 (b), the dotted lines show the contributions of SP2 hybrid orbital coupling and SP3 hybrid orbital coupling, respectively. The dotted line with the left peak is due to the SP3 hybrid orbital coupling, and the dotted line with the right peak is Due to SP2 hybrid orbital coupling.

(Second Embodiment) The hot cathode of this embodiment is one in which diamond particles are formed on a carbon-based thin film. FIG. 3 is a cross-sectional view showing the structure of the hot cathode of this embodiment. As shown in this figure, an amorphous carbon-based thin film 22 is formed on the surface of an electrode material (filament or the like) 21 as a first member made of carbon containing SP2 hybrid orbital bonds. Diamond particles 33 are formed on the carbon-based thin film 22. In FIG. 3, the diamond particles 33 are distributed in a scattered form, but they may be distributed densely or in close contact with each other.

According to the hot cathode of this embodiment, since the diamond particles 33 are formed in a distributed manner, the durability of the hot cathode is slightly deteriorated as compared with the first embodiment. However, exfoliation of the diamond particles 33 caused by thermal expansion and thermal contraction of the hot cathode can be prevented, and the durability of the hot cathode becomes excellent. That is, since the expansion coefficient of the electrode material of the hot cathode is higher than that of diamond,
When the discharge device is operated and the hot cathode is heated, tensile stress is generated in the diamond due to the temperature rise, and in actual use, the discharge device operates and does not operate repeatedly. In this case, there is a potential problem that the diamond peels from the electrode material due to the difference in the coefficient of thermal expansion. In the hot cathode according to the present embodiment, in addition to the above-described improvement in the adhesion between the diamond and the electrode material, stress relaxation due to the gap between the diamond particles 33 can suppress the problem of the diamond peeling.

Next, a method of manufacturing the hot cathode of this embodiment will be described. First, the carbon-based thin film 22 was formed by the same manufacturing method as in the first embodiment. Next, the diamond particles were mixed with an organic solvent such as alcohol, and this solvent was applied to the surface of the carbon-based thin film 22. The diamond particles mixed in the organic solvent had a particle size of 0.1 micron or more and 3 micron or less. For coating, a method of immersing the electrode material 21 having the carbon-based thin film 22 in an organic solvent mixed with diamond particles and performing ultrasonic cleaning was adopted. The treatment time by ultrasonic cleaning was 30 minutes.
By ultrasonic cleaning, the diamond particles were evenly attached to the surface of the carbon-based thin film 22. Then, if necessary, for example, in a nitrogen atmosphere at a temperature of 200 degrees, 60
The heat treatment was performed for minutes to remove the organic solvent and impurities.

(Third Embodiment) The hot cathode of this embodiment is one in which diamond particles are selectively formed on a selectively formed carbon thin film. FIG. 4 is a cross-sectional view showing the structure of the hot cathode of this embodiment. As shown in this figure, on the surface of the electrode material (filament etc.) 21, S
An amorphous carbon-based thin film 42 is selectively formed in an island shape as a first member made of carbon containing P2 hybrid orbital bond. Diamond particles 43 are formed on the carbon thin film 42.
Are formed. In FIG. 4, diamond particles 4
The 3s are distributed in a scattered form, but they may be distributed densely or in a form in which they are in close contact with each other.

According to this embodiment, it is possible to obtain the same effects as those of the above-described embodiments, and at the same time, the carbon-based thin film 21.
It is possible to obtain the effect of stress relaxation.

Next, a method of manufacturing the hot cathode of this embodiment will be described. First, the carbon-based thin film 42 is formed on the electrode material 21.
The carbon-based thin film 42 is formed on the entire surface of the electrode material 21 when forming the
Was not formed, and was selectively formed only in a partial region. The CVD method of diamond was used for the film formation. The conditions for forming the carbon-based thin film shown in the first embodiment were changed. In this embodiment, the microwave power is 50 W, the self-bias using an RF power source is -150 V, and the hydrogen gas (H ₂ ) flow rate is 20 scc.
m, and the flow rate of methane gas (CH ₄ ) was 3 sccm. The pressure was 1 Pa, the temperature was 750 ° C., and the growth time was 1 minute.
When the carbon-based thin film was formed under these conditions, the carbon-based thin film 42 was deposited on the surface of the electrode material 21 so as to be scattered in several microns.

Next, the diamond particles 43 were continuously formed by the microwave plasma CVD method. The formation conditions are
Microwave power 3kW, reaction gas pressure 10kP
a, hydrogen gas flow rate is 500 sccm, methane gas flow rate is 5 sc
cm, the substrate temperature was 850 ° C., and the diamond particles 43 having a particle size of 3 μm or less (typically about 1 μm) were formed in a film forming time of 60 minutes. In this embodiment, the scattered carbon-based thin films 42 serve as nuclei, and the diamond particles 43 grow without being damaged.

(Fourth Embodiment) The hot cathode of the present embodiment forms a carbon-based thin film also between diamond particles. FIG. 5 is a cross-sectional view showing the structure of the hot cathode of this embodiment. As shown in this figure, on the surface of the electrode material (filament or the like) 21, an amorphous carbon-based thin film 52 is selectively formed in an island shape as a first member made of carbon containing SP2 hybrid orbital bonds. Has been done. Diamond particles 53 are formed so as to be embedded in the carbon-based thin film 52. Although the diamond particles 53 are distributed in a scattered form in FIG. 5, they may be distributed densely or in a form in which they are in close contact with each other. According to this embodiment,
The same effect as that of each of the above-described embodiments can be obtained.

Next, a method of manufacturing the hot cathode of this embodiment will be described. First, the film forming conditions for forming the carbon-based thin film 52 by ECRCVD are as follows. That is, the microwave power was 50 W, the self-bias using an RF power supply was -100 V, a mixed gas consisting of a hydrogen gas (H ₂ ) flow rate of 10 sccm and a methane gas (CH ₄ ) flow rate of 1 sccm was used, and the pressure was 1 Pa and the temperature was 750 ° C. The carbon-based thin film 52 having a thickness of 50 nm was formed under the film forming time of 1 minute.

In this embodiment, the reaction gas is hydrogen or methane gas. CO gas or CO ₂ gas may be used as the carbon source. Further, it is possible to dope impurities such as nitrogen and phosphorus, which show n-type, as impurities. In addition, there is no problem even with impurities showing p-type such as boron. Further, the method for manufacturing the carbon-based thin film 52 is the same as the EC shown in the present embodiment.
Not only the RCVD method, but also the radio frequency (RF) CVD method, the ion beam method, or the like can be used for manufacturing.

Next, the diamond particles 53 are continuously formed. That is, the diamond particles 53 are formed by the microwave plasma CVD method in a state where the vacuum atmosphere is maintained while the sample 60 is held in the reaction chamber 63 of the ECRCVD apparatus shown in FIG. In this film formation, the heater stage 61 is heated by the heater power supply 65, and the sample 60 placed on the heater stage 61 is heated.

The film forming conditions for the diamond particles 53 in this case are as follows. That is, microwave power is 4k
W, reaction gas pressure 133 hPa, hydrogen gas flow rate 40
0 sccm, methane gas flow rate 4 sccm, substrate temperature 850 ° C
As a result, diamond particles 53 were formed with a film forming time of 20 minutes. Here, the diamond particles have a dense portion or a contact portion.

Subsequently, the carbon thin film 52 is continuously formed again. ECRCVD was used for fabrication. The forming conditions are the same as those of the previously formed step, but the forming time is set to 60 minutes so as to cover the diamond particles 53. Finally, in order to expose the surface of the diamond particles 53, plasma etching with oxygen was performed. According to the hot cathode of the present embodiment,
The stress relaxation effect of the carbon-based thin film 52 can be obtained, and the adhesion of the diamond particles 53 to the carbon-based thin film 52 can be improved.

(Fifth Embodiment) In this embodiment, an example will be described in which the diamond thin film described above is doped with an impurity exhibiting n-type conductivity. FIG. 9 is a diagram for explaining the principle of this embodiment, and is a band diagram of diamond doped with an n-type impurity. Diamond exists at a position where the vacuum level indicated by Evac is lower than the bottom of the conduction band of diamond indicated by Ec, and NEA (Negative Electron Affinit
It is known to have a negative electron affinity called y). The electron affinity is the energy required to move the electron at the bottom of the conduction band into a vacuum, and having a negative value means that the electron is very easily emitted.

However, n-type doped diamond has extremely high resistance at room temperature, and when diamond is used as a cold cathode, attempts to realize a highly efficient cathode by utilizing its NEA characteristic have not been successful. This is the energy difference Ed between the level of the donor giving the electron and the bottom of the conduction band.
Is more than 10 times that of ordinary semiconductors such as Si, and there are almost no electrons in the conduction band at room temperature.

However, it has been found that by applying the n-type doped diamond to a discharge device such as a fluorescent lamp and heating it, a sufficiently excellent electron emission characteristic is obtained.
In the present embodiment, a hot cathode utilizing such excellent electron emission characteristics and a discharge device having excellent emission characteristics will be described.

When n-type doped diamond is heated as described above, electrons rise to the conduction band as the temperature rises, so that it becomes possible to emit electrons utilizing the NEA characteristic. That is, in the NEA diamond, since there is no barrier that prevents the electrons in the conduction band from being emitted into the vacuum, the energy required to emit the electrons is eventually about Ed. On the other hand, in a normal electron emission material that does not have NEA characteristics, the vacuum level Evac
Is above the bottom Ec of the conduction band, and the energy required to emit electrons into a vacuum has a value around the work function.
Regarding the value of Ed, a value of about 0.6 eV is obtained when phosphorus is doped into diamond, while the value of the work function is BaO which is often used for thermionic emission emitters.
The value is about 1.1 eV. Since these values have an exponential effect on thermionic emission, the n-type doped diamond can emit thermionic electrons at a low temperature. Therefore, in a discharge device such as a fluorescent lamp using such a hot cathode, uniform thermoelectron emission can be realized at a low temperature, thereby providing a hot cathode discharge device having excellent light emission characteristics and long life. You can

Further, the work function is extremely sensitive to the influence of the surface state, and is strongly influenced by the manufacturing process, atmosphere and the like. Therefore, it is difficult to expect uniformity in the electron emission surface.
Since the work function value has an exponential effect on thermionic emission, the inhomogeneity of thermionic emission tends to be large. On the other hand, in the NEA diamond, as long as the electron affinity is negative, even if the value fluctuates to some extent, it does not affect the thermionic emission, and the thermionic emission is determined by the donor level and conduction. It is the energy difference Ed from the bottom of the band. This value is not a surface property, but a bulk property determined by the dopant. Therefore, in n-type diamond, uniform in-plane thermoelectron emission can be expected. Further, diamond has the highest thermal conductivity, and even if there is Joule heat, ion / electron inflow, or heating by impact, the heat is quickly transmitted to the surroundings and the temperature becomes uniform. Sufficient effect can be obtained only by using n-type diamond, but when the form is a uniform continuous film, the effect is great.

Next, the hot cathode and the discharge device according to this embodiment will be described. First, a filament is prepared by winding a tungsten wire having a wire diameter of 30 μm in a coil shape. After washing, the filament is firstly applied as in the first embodiment.
An amorphous carbon-based thin film is formed as a member of. With this carbon-based thin film, the same effect as that of the first embodiment can be obtained.
Further, a polycrystalline diamond layer having a thickness of about 3 microns is formed by, for example, microwave plasma CVD method. The growth conditions of the polycrystalline diamond layer were microwave power of 4 kW, hydrogen flow rate of 200 sccm, methane gas flow rate of 4 sccm, and methane concentration of the source gas was 2%. The pressure of the source gas was 133 hPa, the filament was heated to 850 ° C., and the film formation time was 50 minutes. Phosphorus was used as the n-type dopant, and phosphine gas was simultaneously supplied during diamond growth. The ratio of phosphine gas to methane gas is 1000 ppm
And

After that, an introducing wire for holding the filament and energizing the filament is provided, and a metal fitting is attached to the introducing wire and attached to the glass tube, and sealed with a sealing gas to complete the discharge device.

(Sixth Embodiment) FIG. 8 shows a sixth embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the configuration of the hot cathode according to the embodiment of FIG. As shown in this figure, the hot cathode of the present embodiment is a so-called indirectly heated type in which a heating portion (tungsten layer 81) and a thermoelectron emitting portion (phosphorus-doped polycrystalline diamond layer 84) are separated. Cathode, linear tungsten layer 8
Heating is carried out by energizing No. 1. The phosphorus-doped diamond layer 84 is connected to a lamp circuit (not shown) and is used as a thermionic emission portion. That is, the tungsten layer 81 is formed on the quartz substrate 80 in a folded linear shape, and the upper surface and the side surface of the tungsten layer 81 are covered with the carbon-based thin film 82. The carbon-based thin film 82 is a first member made of carbon containing SP2 hybrid orbital bond, and is an amorphous carbon-based thin film. A non-doped polycrystalline diamond layer 83 is formed on the exposed surface of the quartz substrate 80 and the carbon-based thin film 82, and a phosphorus-doped polycrystalline diamond layer (n-type diamond) is further formed on the polycrystalline diamond layer 83. 84 is formed.

In the hot cathode having the structure shown in FIG. 8, the non-doped polycrystalline diamond layer 83 electrically separates the linear tungsten layer 81 and the phosphorus-doped polycrystalline diamond layer 84. It is used for The hot cathode of the present embodiment takes advantage of the fact that the n-type diamond continuous film can uniformly emit thermoelectrons at a low temperature and has a large thermal conductivity, and since it operates at a low temperature, it has a filament structure. Instead, it is configured as a planar structure with a large electron emission area. In addition to large and uniform thermionic emission, the temperature is uniform due to the large thermal conductivity, so that a large current lamp can be realized.

In the hot cathode having the above structure, the polycrystalline diamond layer 83 is formed on the tungsten layer 81 via the carbon-based thin film 82, and the carbon-based thin film is interposed between the tungsten layer 81 and the carbon-based thin film 82. 82 and the non-doped polycrystalline diamond layer 83, and between the non-doped polycrystalline diamond layer 83 and the phosphorus-doped polycrystalline diamond layer 84, the adhesion is good, so that the polycrystalline diamond layer (83 , 84) can be effectively prevented from peeling off from the tungsten layer 81.

Next, a method of manufacturing the hot cathode of this embodiment will be described. First, a quartz substrate 80 is prepared, and after cleaning the quartz substrate 80, a tungsten layer 81 is formed thereon by a sputtering method and then processed by photolithography to form a linear tungsten layer 81 having a width of 30 μm. Formed. Further, the carbon-based thin film 82 was selectively formed on each of the upper surface and the side surface of the tungsten layer 81 under the same conditions as in the first embodiment. Under these conditions, the carbon-based thin film 82 did not adhere to the exposed surface of the quartz substrate 80. Next, the same conditions as in the fifth embodiment (when the non-doped polycrystalline diamond layer 83 is formed, phosphorus as the n-type dopant is not used, and the phosphorus-doped polycrystalline diamond layer 84 is formed). In the case of using phosphorus as an n-type dopant, the microwave plasma is used.
The non-doped polycrystalline diamond layer 83 is formed by the CVD method.
A phosphorus-doped polycrystalline diamond layer 84 was continuously formed. The thickness of the polycrystalline diamond layer 83 is 1 μm
The polycrystalline diamond layer 84 has a thickness of about 5 μm. The hot cathode of this embodiment is manufactured through the above steps.

In this embodiment, the carbon thin film 82 is used.
Although it is formed on each of the upper surface and the side surface of the tungsten layer 81, it may be formed only on the upper surface of the tungsten layer 81 or only on the side surface of the tungsten layer 81. In the former case, the tungsten layer 81 and the carbon-based thin film 82 can be formed by continuously forming them and then processing them by photolithography. On the other hand, in the latter case, after processing the tungsten layer 81, the carbon-based thin film 8 is
It is possible to selectively leave the carbon-based thin film 82 on the side surface of the pattern of the tungsten layer 81 by forming 2 thickly on the entire surface and anisotropically etching the carbon-based thin film 82.

(Seventh Embodiment) In this embodiment, a hydrogen gas for discharge to be enclosed in a hot cathode fluorescent lamp (discharge lamp) according to the discharge device of the present invention will be described. The surface of a diamond produced by chemical vapor deposition (CVD) using a so-called hydrogen-based gas as a carrier gas is generally terminated by hydrogen. This hydrogen termination layer greatly contributes to the characteristics of diamond, and plays an important role in exhibiting the NEA characteristics described above. Therefore, it becomes possible to emit thermoelectrons from diamond from a low temperature. However, when the temperature rises to a certain degree, the desorption of hydrogen terminating the diamond surface begins. The hot cathode according to the present embodiment is also characterized in that this desorption of hydrogen is suppressed.

Next, the structure of the hot cathode fluorescent lamp according to this embodiment will be described. In this embodiment, the hot cathode in which the carbon-based thin film 22 and the polycrystalline diamond layer 23 are sequentially formed as described in the first embodiment is used, but the hot cathode of other embodiments or diamond is used for other surfaces. It is also possible to employ a hot cathode that has been used. Argon gas and hydrogen gas were used as the filling gas in the hot cathode fluorescent lamp. Argon gas was filled with gas at a partial pressure ratio of 4 hPa, and hydrogen gas was filled with gas at a partial pressure ratio of 1 Pa. For comparison, a hot cathode discharge lamp without hydrogen gas was also manufactured. As a result of comparing the two, it was confirmed that the life of the hot cathode in the discharge lamp filled with hydrogen gas was significantly improved. It is considered that this is because it was possible to suppress the desorption of hydrogen on the diamond surface of the hot cathode by enclosing the hydrogen gas.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. For example, the electrode material is not limited to tungsten, but other materials such as molybdenum can be used. Further, the shape of the electrode is not limited to the coil or the linear shape, and it is possible to adopt a plate shape, a film shape or the like, for example.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0071]

According to the present invention, it is possible to effectively prevent the problem that the diamond member is separated from the electrode, and it is possible to greatly improve the durability of the discharge device.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structure of a hot cathode discharge lamp according to a discharge device of the present invention.

FIG. 2 is an enlarged sectional view showing a configuration of electrodes 11a and 11b of FIG.

FIG. 3 is a sectional view showing the structure of a hot cathode according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing the structure of a hot cathode according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a hot cathode according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a film forming apparatus used for forming a diamond thin film and a carbon-based thin film.

FIG. 7 is a characteristic diagram showing the relationship between Raman shift and strength of the diamond thin film and the carbon-based thin film of the present invention.

FIG. 8 is a sectional view showing the structure of a hot cathode according to a sixth embodiment of the present invention.

FIG. 9 is a band diagram of diamond when a diamond thin film is doped with an impurity exhibiting n-type conductivity.

FIG. 10 is a sectional view showing the structure of a conventional general hot cathode discharge lamp.

11 is an enlarged cross-sectional view showing the configurations of electrodes 101a and 101b in FIG.

[Explanation of symbols]

10 ... Glass tube 11a, 11b ... a pair of electrodes 11c, 11d ... Introduction line 12 ... Phosphor 13 ... Sealing gas 14a, 14b ... a pair of metal fittings 21 ... Electrode material 22, 42, 52 ... Carbon thin film 23 ... Diamond thin film 33, 43, 53 ... Diamond particles 60 ... Sample 61 ... Heater stage 62a ... Microwave head 62b ... Microwave waveguide 63 ... Reaction chamber 64 ... Quartz window 65 ... Reaction gas inlet 66 ... Exhaust system 67 ... Upper electromagnetic coil 68 ... Lower electromagnetic coil 69 ... Heater power supply 80 ... Quartz substrate 81 ... Tungsten layer 82 ... Carbon thin film 83 ... Non-doped polycrystalline diamond layer 84 ... Phosphorus-doped polycrystalline diamond layer 100 ... Glass tube 101a, 101b ... A pair of electrodes 101c, 101d ... Lead-in line 102 ... Phosphor 103 ... Sealing gas 104a, 104b ... a pair of metal fittings 105a ... Electrode material 105b ... Diamond particles

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tadashi Sakai             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center (72) Inventor Mariko Suzuki             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center F-term (reference) 5C015 EE01 PP05

Claims (18)

[Claims] 1. An electrode and an SP provided on the surface of the electrode
A first member made of carbon containing two hybrid orbital bonds, and a second member made of diamond provided on the surface of the first member.
A hot cathode comprising: 2. The hot cathode of claim 1, wherein the carbon of the first member also includes SP3 hybrid orbital bonds. 3. The hot cathode according to claim 1, wherein the first member is made of amorphous carbon. 4. The hot cathode according to claim 1, wherein the first member is provided on the entire surface of the electrode. 5. The hot cathode according to claim 1, wherein the second member contains diamond particles. 6. The hot cathode according to claim 5, wherein carbon containing SP2 hybrid orbital bond is provided between the diamond particles. 7. The hot cathode according to claim 1, wherein the second member is made of diamond containing a donor impurity. 8. A discharge device comprising an envelope in which a discharge gas is sealed, and a hot cathode arranged in the envelope, wherein the hot cathode is an electrode and a surface of the electrode. And a first member made of carbon containing SP2 hybrid orbital bond,
A discharge device, comprising: a second member made of diamond and provided on the surface of the first member. 9. The cold cathode discharge device according to claim 8, wherein the discharge gas contains a gas containing an element having a main emission peak of 200 nm or less. 10. The discharge device according to claim 8, wherein the discharge gas contains a rare gas and mercury. 11. The discharge device according to claim 8, wherein the discharge gas contains Xe. 12. The discharge device according to claim 8, wherein the discharge gas contains hydrogen gas. 13. The discharge device according to claim 8, wherein the carbon of the first member also includes an SP3 hybrid orbital bond. 14. The discharge device according to claim 8, wherein the first member is made of amorphous carbon. 15. The hot cathode according to claim 8, wherein the first member is provided on the entire surface of the electrode. 16. The hot cathode according to claim 8, wherein the second member contains diamond particles. 17. SP2 between the diamond particles
The hot cathode according to claim 16, wherein carbon having a hybrid orbital bond is provided. 18. The second member is composed of diamond containing a donor impurity.
18. The hot cathode according to any one of 1 to 17.